Ti substituted for Sc in nano-grain and single crystal complex oxide d<sup>0</sup> GdScO<sub>3</sub> films is incorporated in a trivalent state, Ti<sup>3+</sup>, creating a mixed d<sup>0</sup>-d<sup>1</sup> oxide with composition-dependent transport properties, including an insulator to metal transition for compositions in which Ti exceeds a percolation threshold of ~ 16%. X-ray absorption spectroscopy has been used to study occupied electronic states of the Ti<sup>3+</sup> atoms, and final states for 2p to 3d core level excitations, O 1s core level excitations to virtual conduction band states, intra d-level excitations, and resonant photoemission. These spectrocopies are interpreted in the context of many electron transitions and distinguish between spin alignment in nano-grain films, and single crystal films identifying hopping-induced multi-mixed valency on Ti and Si sites in “Sc-oxide” planes. Inter-atomic transport provides a novel approach to modulate ferromagnetism associated with a double exchange mechanism.
i) O K edge X-ray absorption: Comparisons between nano-grain, and epi-thin films demonstrates differences in spin-up and spin-down correlation energy split bands. Second derivative pre-edge spectra indicate a strong spin-up band at low energy, and a weaker spin-up band separated by ~ 1eV in the epi-films. Randomly orientated nano-grains with dimensions < 3 nm, result in a single broad feature that spans width of the two bands in the epi-films.
ii) Ti and Sc L<sub>2,3</sub> spectra for occupied 2p core levels to 3d levels, have identified differences between spectra in alloy films above and below the percolation threshold. Interpretations in the context of many electron charge transfer multiplet methods has identified the steady-state transfer of electrons between occupied Ti<sup>3+</sup>, and empty Sc<sup>3+</sup>, states by an intra-layer steady state hopping process: Ti<sup>3+</sup>, + Sc<sup>3+</sup>, >/< Ti<sup>4+</sup>, + Sc<sup>2+</sup>, equivalently, Ti d<sup>1</sup> + Sc d<sup>0</sup> >/< Ti d<sup>0</sup> + Sc d<sup>1</sup>.
iii) Resonant photoemission spectroscopy, energy analyzing photoemitted electrons, indicate two resonances for Ti L<sub>2,3</sub> and Sc L<sub>2,3</sub> edge valence band spectra. These are distinguished by different energies within the occupied states of the valence band. The Ti L<sub>2,3</sub> spectra indicate a resonances above GdScO<sub>3</sub> valence band: the Ti<sup>3+</sup> occupied level, and another within the valence band and assigned to Ti<sup>4+</sup>. The Sc L<sub>2,3</sub> spectra indicate two resonances as well; one associated with decrease in the concentration of occupied Sc<sup>3+</sup> states, and the second with increase the concentration Sc<sup>2+</sup> occupied states. These changes are consistent charge exchange: Ti d<sup>1</sup> + Sc d<sup>0</sup> >/< Ti d<sup>0</sup> + Sc d<sup>1</sup>.
Finally, the results of this paper indicate the two conditions necessary for double exchange ferro-magnetism, are met by alloying in Ti in Gd(Sc,Ti)O<sub>3</sub>: (i) mixed valency of in-plane Ti and Sc atoms, and (ii) hopping transport metallic conductivity. Inter-atomic transport then provides
a novel way for current controlled double exchange ferromagnetism.